Safety device



Aug. 5, 1941. c. A. RISING EI'AL SAFETY DEVI CE Filed April 26, 1959 FIG.5.

CALVIN A RISING J. DONALD MAC Kmsnr INVENTORS BY% ATTORNEYS Patented Aug. 5, 1941 UNITED STATES SAFETY DEVICE Calvin A. Rising and John Donald MacKnight, Mount Vernon, N. Y., assignors to The Texas Company, New York, N. Y., a corporation of Delaware Application April 243, 1939, Serial No. 270,045

3 Claims.

This invention relates to improvements in safety devices, and more particularly to a device for closing an electric circuit when the wall of a tube or vessel has become corroded or eroded to a predetermined thickness.

In the operation of stills or vessels where superatmospheric pressures and temperatures are employed, such as in the cracking of hydrocarbon oils, the walls of the stills and heater tubes often become reduced in thickness due to the corrosive or erosive nature of the fluids being handled. Frequently the vessels are operated when portions of the Walls thereof become worn beyond a safe operating thickness due to the fact that these portions escape detection when the vessels are down for cleaning and inspection. Or, while the entire Walls of the vessel may be of suflicient thickness at the time of inspection, due to the highly corrosive nature of some particular charge, portions of the walls of the vessel may be attacked more severely than anticipated, and failure of the vessel may sult. Such hazards to life and property as are presented by these conditions arewell known to the industry.

The principal object of this invention is to provide a device which will close an electric circuit so as to signal an operator when a portion of a tube or vessel wall has become Worn beyond a safe operating thickness.

Other objects and advantages of the invention will become apparent during the course of the following description,

It is recognized that openings have heretofore been drilled part way through tube walls and other parts of oil cracking apparatus to induce localized failure thereof, so that when the wall of the vessel or tube has become corroded to a predetermined thickness due to the corrosive or erosive character of the fluid, some of the fluid in the tube will be released in a small stream whereupon an operators attention will be directed to the failure. If the failure is inside a heater the oil may become ignited, giving a different color flame from that produced by the fuel oil employed in heating the tubes. or the weakened condition may be indicated by smoke issuing from the stack of the furnace.

In accordance with the present invention. there is provided a pressure responsive. electrical contact device formed as a hollow plug adapted to be positioned within or over an opening or well of small diameter extending part way through the wall of a tube or vessel shell, the plug serving to support a plunger, plunger rod and electric contacts and the arrangement being such that when the tube wall has been corroded or otherwise worn away to the point where the fluid in the tube or vessel flows into the plug, the pressure thus created will force the plunger outwardly closing an electric circuit and thereby activating an alarm or other signaling device.

The invention will be more fully understood from the following description in conjunction with the accompanying drawing illustrating pre ferred embodiments of the invention and forming a part of this specification.

Figure 1 is a plug in fragmental section posi tioned in a portion of the wall of a vessel, also shown in section.

Figures 2, 3 and 4 are views in fragmental section of plugs embodying modifications of the invention.

Figure 5 is a plug in fragmental section positioned over a well extending part way through a vessel wall.

Figures 6 and 7 are views in perspective of a section of a vessel having recesses extending part way therethrough and being provided with a cover member thereover containing one or moi of the plugs forming a part of the invention.

Referring to Figure 1 of the drawing, a section of a vessel wall Ill is shown having a threaded plug l2 screwed into an opening or well M of the vessel wall. If desired, the plug can be welded to the vessel wall after it is inserted and in that case may not be threaded. A plunger 16 having a collar 2'8 is adapted to slide through an opening 22 in said plug and extends into a recess 2| in the plug. A spring 24 is secured to the plug or to the outside wall of the vessel at a point adjacent the plug to retain the plunger in a normally inward position. Other means for holding the plunger in a normally inward position could obviously be employed, such for example as by inserting a small spring or piece of steel wool around the plunger rod between the plunger and the top of the recess. In the event the vessel wall becomes reduced in thickness by corrosion and/or erosion, as shown by the broken line l9, to the extent that fluid flows into the recess 2!, the pressure of the fluid will force the plunger outwardly, causing the plunger rod to engage an electrical contact member 26 and close a circuit 28 which includes a source of electricity 3% and an alarm 32, the circuit being completed or grounded through. wall is at the point The contact 26 is insulated from the plug it or vessel wall I!) by a suitable insulation 35. The circuit may be employed to actuate remotely controlled valve, not shown, for closing off the supply of fuel used in heating the or to otherwise signal an operator when the circuit has been completed.

In Figures 2 and 3 there are illustrated two modifications of the invention in which like numerals are employed to designate corresponding parts. A plug in is provided with a recess 2m housing a collapsible or compressible member 38 containing contacts 40 and 42, the movable contact 40 being connected by a wire 44 passing through the opening 220., which may be porcelain lined or otherwise insulated, to an alarm system as described in connection with Figure 1. In Figure 2, one side of the compressible member 38 is formed in an insulating member 45 housed within the recess 2 la and in Figure 3 the surface of the plug at the inner end of the recess Zla forms one side of the compressible member and supports the contact 42. The other sides of the compressible members as shown in both Figures 2 and 3 are preferably formed of thin sheet metal so that they can be compressed by a fluid under pressure. Thus, when oil or other liquid or fluid under pressure flows into the recess 21a due to the corrosion or erosion of the tube wall, the member 38 will be compressed, causing the circuit to be closed through contacts 38 and 42 to signal an operator.

Referring to the modification as illustrated in Figure l, a plug l2b provided with a recess Zib is shown in position within a portion of a vessel wall ID. A helical spring 48 housed within the recess Zlb is secured to a compressible member 50 in a manner such that the free end of the spring 48 is abutting the vessel wall Iii. A contact member 52 secured to the wall of the recess 2| 1) and insulated therefrom is connected by Wire 54 passing through an opening 22b in the plug [2b to an electric circuit such as the circuit 28 hereinbefore described in connection with Figure 1. Normally the member 50 is under compression of the spring 48 but in the event the wall of the vessel becomes worn through at the recess, the spring 48 will be released, allowing the member 50 to expand and engage the contact member 52 to thereby close the circuit of the alarm system. While extremely high temperatures may possibly remove the temper from the spring 48, the modification as shown in Figure 4 may be utilized to advantage in a system handling acid or other corrosive fluid where such high temperatures are not likely to be employed.

As illustrated in Figure 5, a plug 53 as hereinbefore described in connection with either Figure 1, 2 or 3 may be positioned over a well or opening 55 in a vessel wall 58 and held in place by welding it to the vessel wall. This modification will present advantages in that a plug of any suitable size can be mounted over an opening of extremely small cross-sectional area, thereby minimizing any danger incident to the localized reduction in the strength of the vessel. If desired, a cap 68 can be suitably attached to the vessel wall so as to enclose and protect the contact device.

Referring to Figure 6, there is shown a section of a tube 68 provided with a narrow groove or slot 62 extending part way therethrough and which may extend for any desired length of the tube. A metal cover plate 54 of sufficient thickness to withstand fairly high pressure for at least a short period of time and closed at both ends to form a fluid-tight chamber 66 is welded over the groove 62 to the tube wall 68. A contact device 68 such as is shown in Figure 1, 2 or 3 is positioned within an aperture in the cover plate 64, and when sufiicient pressure produced by the fluid is built up within the chamber 68 the electric circuit will be closed to provide a signal as hereinbefore described.

Instead of providing the tube 68 with a groove or slot, wells or openings Til may be drilled part way through the tube at spaced intervals and the cover plate 64 welded thereover to the tube to form a fluid-tight chamber 72 as illustrated in Figure 7 and a contact device M as described above in connection with Figure 1, 2 or 3 inserted into the cover plate and connected in an electrical circuit as shown in Figure 1. With the modifications as shown in Figures 6 and 7, a single contact device may serve a larger area of a vessel wall or tube, the cover plate B l reinforcing the tube at the points where the groove or holes are placed.

While the invention may have utility in various industries handling corrosive fluids, it has particular utility in petroleum cracking and distillation apparatus. In the operation of a cracking vessel corrosion or erosion of a tube occurs to the greatest extent near the ends which are inserted into the header box. The portion of the header box forming the return bend is also materially affected by the corrosive action of the fluid passing therethrough. Pressure responsive contact devices for closing an electrical circuit in accordance with the present invention may very advantageously be located at these particular points.

Obviously many modifications and variations of the invention as above set forth may be made without departing from the spirit and scope thereof, and therefore only such limitations should be imposed as are indicated by the appended claims.

We claim:

1. An electrical circuit closing device adapted to be actuated by the pressure exerted by fluid tending to escape through an opening in a vessel wall, which comprises a plug disposed within said opening, a member slidably disposed through said plug, resilient means for normally retaining said member a predetermined distance within said plug, and an electrical contact member positioned opposite the outer end of said slidable member and adapted to be engaged by said member on a predetermined increase in pressure in said opening.

2. An electrical circuit closing device adapted to be actuated by the pressure exerted by fluid passing through an opening within a vessel wall, which comprises a plug disposed within said opening, a plungor slidably disposed through said plug, resilient means for normally retaining said plunger a predetermined distance within said plug, and an electrical contact member positioned in the path of the outer end of said plunger, the arrangement being such that on a predetermined thinning of the wall of said vessel the fluid will enter said opening and force said plunger outwardly to engage said electrical contact member to complete said electrical circuit.

3. An electrical circuit closing device adapted to be actuated by the pressure exerted by fluid passing through an opening in a vessel wall, which comprises a plug disposed substantially entirely within said opening and having a recess in its inner end thereof, a plunger slidably disposed through said plug with one end thereof extending into said recess, resilient means for normally retaining said plunger a predetermined distance within said plug, and an electrical contact member positioned opposite the outer end of said plunger and adapted to be engaged by said plunger on a predetermined increase in pressure in said recess.

CALVIN A. RISING. JOHN DONALD MACKNIGHT. 

